test: Add more retry to client-testing.

Author: timoxley

.github/workflows/test-build.yml

@@ -220,7 +220,7 @@ jobs:
       - uses: nick-invision/retry@v2
         name: run-client-testing
         with:
-          max_attempts: 2
+          max_attempts: 3
           timeout_minutes: 15
           retry_on: error
           command: cd streamr-client-testing && DEBUG='' java -jar build/libs/client_testing-1.0-SNAPSHOT.jar -s $TEST_NAME -c config/$CONFIG_NAME.conf -n $NUM_MESSAGES